A chain mediation model reveals the association between family sense of coherence and quality of life in caregivers of advanced cancer patients

Caregivers of advanced cancer patients face challenges impacting their quality of life (QoL). While evidence suggests that family sense of coherence (FSOC) can enhance individual psychological well-being and reduce distress symptoms, the precise mechanism through which FSOC improves caregivers' QoL remains unclear. This study aimed to explore the relationships among FSOC, psychological resilience, psychological distress, and QoL in primary caregivers of advanced cancer patients. A cross-sectional observational study was undertaken from June 2020 to March 2021 across five tertiary hospitals in China. Instruments included a general characteristic questionnaire, the Family Sense of Coherence Scale, the Patient Health Questionnaire-4, the 10-item Connor–Davidson Resilience Scale, and the 8-item SF-8 health survey. Pearson’s correlation and chain mediation analyses were performed using IBM SPSS (version 21) and PROCESS macro (version 3.4). Out of 290 valid questionnaires, results demonstrated that FSOC directly and positively influences caregivers' QoL. Psychological distress partially mediated the FSOC-QoL association, with paths "FSOC-psychological distress-QoL" and "FSOC-psychological resilience-psychological distress-QoL" contributing 43.08% and 6.72% of the total effect, respectively. Furthermore, this study distinguished physical and mental aspects of QoL, confirming both conform to the chain mediation model. FSOC impacts caregivers' QoL directly and indirectly through the mediation of psychological distress and the chain mediation effect of "psychological resilience-psychological distress". These insights enhance our understanding of the complex interplay between FSOC and QoL, underscoring the potential benefits of bolstering FSOC to strengthen caregiver resilience, alleviate distress, and ultimately elevate their QoL.


The mediating role of psychological resilience
The intricate mechanisms underlying how FSOC influences QoL warrant further investigation, with psychological resilience potentially acting as a mediator.Psychological resilience is characterized by an individual's adeptness in navigating adversity, trauma, or threats 18 .It emphasizes an individual's capability to adapt, rebound, and sustain mental equilibrium in the face of life's multifaceted challenges.Such resilience not only facilitates navigation through tough scenarios but also fosters the maintenance of a positive emotional state, enabling preservation or restoration of regular life functions.This makes psychological resilience a pivotal protective factor for QoL.
A recent systematic review elucidated that caregivers of advanced cancer patients initiate their psychological resilience process from the point of diagnosis, which could culminate in psychological well-being, benefit finding, and personal growth 19 .The coping strategies employed by caregivers throughout the caregiving trajectory represent a spectrum of means to modulate this resilience process.Within this spectrum, FSOC emerges as a significant family-level coping strategy.While the nexus between FSOC and individual psychological resilience has yet to be extensively probed, studies focused on psychological resilience in cancer patients have underscored a robust positive correlation between individual-level sense of coherence and resilience 20,21 .The dynamic between family-level sense of coherence and psychological resilience, however, remains ambiguous.
Theoretically, caregivers boasting higher degrees of FSOC likely benefit from fortified emotional bonds within the family 14 .Such bonds can imbue caregivers with amplified confidence and fortitude to tackle caregiving challenges.This cohesive family environment at the familial level might also bolster unity in patient care, fostering collective optimism, motivation, and hope 17 .In turn, this can boost caregivers' psychological resilience, augmenting their QoL.Consequently, we posits Research Hypothesis 2: FSOC exerts a direct influence on QoL, with psychological resilience serving as a partial mediator in this dynamic.

The mediating role of psychological distress
Psychological distress presents as a form of psychological discomfort that may affect an individual's emotions, behaviors, and daily functioning.It stands as a critical determinant of the QoL for caregivers of advanced cancer patients.Previous studies attest that such caregivers frequently grapple with elevated levels of psychological distress, encompassing symptoms like anxiety and depression 22,23 .These emotional strains can be attributed to the multifaceted responsibilities of caregiving, the patient's deteriorating health, and the uncertainties looming about the future 24 , often varying in tandem with the patient's physical well-being 25 .
Evidence reveals that manifestations of psychological distress can markedly undermine caregivers' QoL across several facets, including physical and mental health, social interactions, and holistic well-being 26 .The erosion in QoL due to these mental health challenges might stem from the onerous demands of caregiving, the emotional toll of witnessing patient suffering, feelings of despondency and impotence amidst dim recovery prospects for the patient, a paucity of social support systems for emotional unburdening, and the sidelining of self-care in favor of patient-centric concerns, among other dynamics 27 .
FSOC, as a family-level coping mechanism, encapsulates the collective cognizance of the stress induced by advanced cancer 14 , the conviction in harnessing familial resources to navigate this stress, and the discernment

Participants and procedure
For inclusion in the study, advanced cancer patient caregivers had to meet the following criteria: (1) They provided care for stage IV cancer patients aged 18 or above; (2) They themselves were at least 18 years old; (3) Patients identified them as their main, non-professional caregiver; (4) They willingly gave informed consent.However, those caregivers with severe mental or physical health issues were not considered.Targeting a participant group of over 200, in line with recommendations for structural equation modeling 37 , 330 caregivers were approached, and 290 agreed to be part of our study.
The recruitment process utilized convenience sampling executed by five skilled research assistants, all registered nurses, each affiliated with a distinct hospital.If participants struggled with the survey, these assistants

Statistical analysis
Descriptive analysis was performed to scrutinize the data.All demographic variables, including gender and education level, were categorized and summarized using frequencies and percentages.Continuous variables, such as scale scores, were expressed as means with standard deviations (mean ± SD).To investigate the interrelationships between different variables, Pearson correlation analysis was utilized.The impact of various factors on the QoL and its specific domains for caregivers was assessed using independent t-tests and one-way ANOVA where appropriate.Further analysis entailed a chain mediation using PROCESS 3.4 macro within SPSS 21.0, selecting Model 6.In this analysis, FSOC was the independent variable, with QoL-encompassing the physical and mental health domains-as the dependent variables, while psychological resilience and psychological distress served as mediators.Control variables included any statistically significant characteristics from the univariate analysis.The Bootstrap method, with a sample size of 5000, was employed to assess mediation effects 45 .A mediation effect is deemed significant if its confidence interval does not encompass 0. For the purposes of this study, a significance level of P < 0.05 was adopted, with α designated for a two-tailed test.

Common method deviation test
Harman single-factor test was performed to check for common method bias 46 .The results showed that there were 7 factors with characteristic roots greater than 1, and the variance explained by the first factor was 29.13%, less than the critical standard of 40%.Therefore, there are no serious common methodological biases in this study and it can be continued.

Descriptive statistics
Out of the 300 returned questionnaires (90.9%), 290 (representing 87.9%) were found to be valid for analysis.
Table 1 shows the demographic characteristics of the subjects and a univariate analysis of QoL scores and their sub-dimensions across various characteristics.The mean age was 55.4 years for patients and 44.6 years for caregivers.Female caregivers made up 52.1% of the sample, and most were married.On the employment front, 43.8% of the caregivers had jobs.Nearly half, or 49.7%, indicated a monthly per capita household income exceeding 3000 RMB, and 50.7% hailed from rural settings.In the patient group, 76.2% had been diagnosed primarily with a solid tumor, and the median duration post-advanced cancer diagnosis was eight months.Approximately half of the caregivers had dedicated a minimum of 6 months to patient care.Statistically significant differences were observed in caregivers' QoL and physical health scores relative to education level, working status, the presence of chronic diseases, monthly income, and prior caregiving experience (P < 0.05), while working status and monthly income showed significant differences in the mental health scores of caregivers (P < 0.05).Notably, a strong negative correlation was observed between psychological distress and QoL and its sub-dimensions (r = − 0.641 to − 0.499, P < 0.01).These significant correlations among variables support the investigation of subsequent hypotheses.To address concerns about the high correlation between psychological distress and the mental health dimension in QoL possibly being due to correlated items in the two scales, additional correlation analyses were conducted between the four items of psychological distress and two dimensions of QoL.The results indicated that all four items of the PHQ-4 scale exhibited a significant negative correlation with both the mental health and physical health dimensions of QoL, not solely due to the high correlation between psychological distress and the mental health dimension.
The mediation analysis elucidated that psychological distress partially mediates the relationship between FSOC and QoL, where FSOC impacts QoL via two pathways: (a) FSOC → Psychological distress → QoL, (b) FSOC → Psychological resilience → Psychological distress → QoL, with mediating effects calculated at 0.218 [(− 0.073) × (− 2.992)] and 0.034 [0.236 × (− 0.049) × (− 2.992)], respectively.Similarly, psychological distress also partially mediates the relationship between FSOC and both physical and mental health.For physical health, the two pathways identified were Decomposition of effects in Table 5 reveals that the direct effect (0.242) and the total indirect effect (0.264) accounted for 47.83% and 52.17% of the total effect (0.506), respectively.Within the total indirect effect (0.264), the mediation effect of psychological distress and the chain mediation effect of psychological resilience and psychological distress accounted for 43.08% and 6.72% of the total effect, respectively.Table 6 presents the decomposition of effects for FSOC on the sub-dimensions of QoL.In the domain of physical health, the total effect of FSOC was 0.494, with the total indirect effect comprising 42.71% of this effect; specifically, the mediation effect of psychological distress accounted for 34.21%, and the chain mediation effect of "psychological resilience → psychological distress" accounted for 5.46%.Regarding the mental health domain, the total effect of FSOC was 0.501, with the total indirect effect constituted 63.07% of this effect.Within this, the mediation effect of psychological distress contributed 52.09%, while the chain mediation effect of "psychological resilience → psychological distress" accounted for 9.78%.

Discussion
This research presents a chain mediation model to elucidate the underlying mechanisms connecting FSOC and QoL among caregivers of advanced cancer patients.Our findings reveal that psychological distress partially mediates the FSOC-QoL relationship.Additionally, a combined chain mediation effect is observed with both Table 1.Univariate analysis of quality of life and its sub-dimensions of caregivers with different characteristics (N = 290).SD standard deviation.For dichotomous variables, independent samples t tests were used while oneway ANOVA was used for variables with three or more categories.*P < 0.05; **P < 0.01.

The direct effect of FSOC on QoL
This study reveals that, even after controlling for variables, FSOC continues to have a significant direct positive effect on the QoL among caregivers of advanced cancer patients.Elevated FSOC levels correlate with higher QoL scores, indicating an improved QoL for caregivers.In contrast, a previous study by Möllerberg 17 recorded an FSOC score of 68.3 ± 10.8 for caregivers of patients in the palliative phase of cancer.Our study yielded a score of 59.50 ± 11.24, which is lower.This discrepancy might stem from the inclusion of patients in earlier cancer stages in Möllerberg's research, whereas our study specifically targeted stage IV cancer patients.This specialization may result in elevated stress levels for families, manifesting in diminished FSOC scores.Existing research underscores the impact of FSOC on the QoL of infertility-afflicted couples 47 , particularly concerning their mental health.Furthermore, FSOC has been pinpointed as a mediator in the relationship between stress and QoL 16 .Another study by Nagi 48 emphasized the role of FSOC in fostering a sense of meaning

The mediating role of psychological resilience and psychological distress between FSOC and QoL
In addition to the observed direct effects, this study identified a partial mediating role of psychological distress between FSOC and QoL.Caregivers of advanced cancer patients, faced with intense caregiving duties and the challenges of a deteriorating patient condition and future uncertainties, often manifest elevated psychological distress levels 22,23 .Established research underscores the pronounced negative correlation between caregivers' psychological distress and their QoL 49 .FSOC has been documented to bolster an individual's hopefulness and exhibits a substantial negative association with anxiety and depressive symptoms 17 .Grounded in social support theory, familial support invariably results in enhanced individual health outcomes, inclusive of psychological well-being 50 .Within this context, FSOC emerges as an essential familial coping mechanism, correlating with diminished psychological distress among caregivers perceiving heightened FSOC.This is congruent with prior studies exploring the nexus between individual sense of coherence and distress 51 as well as FSOC's relationship with depression 52 .Drawing on theory and previous research, FSOC may improve caregivers' psychological distress in several ways: (1) by providing emotional support and understanding, thereby alleviating the stress of coping with caregiving tasks; (2) by offering methods to cope with and manage stressors related to advanced cancer, helping Table 5.Effect decomposition of family sense of coherence on quality of life.CI confidence interval, FSOC family sense of coherence, PD psychological distress, PR psychological resilience, QoL quality of life.The model was adjusted for caregivers' education level, working status, average monthly family income per capita, the presence of chronic diseases and the previous caregiving experience.6. Testing the mediating effects of the two dimensions of quality of life (physical health, mental health).CI confidence interval, FSOC family sense of coherence, PD psychological distress, PR psychological resilience.The model for physical health was adjusted for caregivers' education level, working status, average monthly family income per capita, the presence of chronic diseases and the previous caregiving experience, while the model for mental health was adjusted for caregivers' working status and average monthly family income per capita.

Model pathways Effect value Total effect ratio Boot 95% CI Significance
Direct effect www.nature.com/scientificreports/caregivers better handle their tasks and challenges.This aligns with other research findings regarding the negative relationship between an individual's sense of coherence and caregiving burden [53][54][55] .Moreover, (3) FSOC can guide caregivers to view the stressors of advanced cancer from a positive perspective, find meaning in them, and set goals.This, in turn, inspires caregivers to proactively mobilize internal and external resources to cope with challenges, a finding consistent with research in infertility couples 48 .In essence, this study posits that enhanced FSOC could lessen the experience of psychological distress, and caregivers with diminished psychological distress are more likely to report improved QoL, characterized by greater physical and mental well-being.In clinical practice, emphasizing and strengthening FSOC among caregivers can be seen as a crucial strategy to alleviate their psychological distress and enhance their QoL.By fostering a more harmonious, supportive, and understanding family environment, caregivers can experience improved psychological well-being, diminished caregiving strain, and a more effective fulfillment of caregiving duties.
Our research indicates that FSOC can serve as a positive predictor for caregivers' psychological resilience.This finding aligns with prior studies highlighting a positive correlation between an individual's sense of coherence and resilience 20,21 .FSOC embodies the positive interactions, mutual support, and understanding prevalent among family members.Such familial cohesion bolsters caregivers' confidence, enabling them to effectively navigate the complexities and challenges posed by advanced cancer 56 .Furthermore, FSOC correlates with positive emotional experiences, enhancing caregivers' psychological resilience.Contrarily, our findings suggest that psychological resilience does not exhibit a statistically significant predictive effect on QoL, diverging from previous studies 57 .The study also determined no notable mediating influence of psychological resilience on the relationship between FSOC and QoL.Potential reasons for these discrepancies could be the utilization of different measurement tools in our study or variations in the cancer severity among patients under the care of these caregivers.Notably, earlier study overlooked factors such as cancer stage, progression, and patient-specific characteristics 57 .To fully understand these disparities, further investigation is warranted.
FSOC may indirectly affect QoL by the chain mediating effects of psychological resilience and psychological distress.Our analysis demonstrates that FSOC significantly forecasts enhanced psychological resilience, which in turn inversely correlates with anxiety and depression.Consequently, this promotes better physical and mental health outcomes.This aligns with previous research findings, indicating that, through stress management interventions by bolstering resilience, the psychological distress and QoL of adolescent and young adult cancer survivors can be significantly improved, with these positive effects lasting at least 2 years 35 .It is posited that caregiver optimism and hopefulness increase when there is perceived family unity, thereby enhancing their psychological resilience and their ability to cope with the challenges of advanced cancer care 58 .This enhancement may manifest in proactive coping, a positive outlook, and improved problem-solving abilities 59 , which collectively diminish psychological distress and, thus, elevate QoL.
Moreover, a robust FSOC offers essential psychological backing to caregivers, fostering a profound sense of support and understanding.Our research indicates that the influence of FSOC on QoL via the "psychological resilience → psychological distress" pathway is less substantial than the direct effects of psychological distress.According to stress appraisal theory, individuals assess potential threats and their resources in response to stress 60 .FSOC, reflecting family support, provides emotional relief to caregivers, directly diminishing their psychological distress as they sense increased family unity.Conversely, while psychological resilience-an innate capacity to rebound from adversity 18 -is beneficial for managing stress, its direct effect on QoL may not be as immediate as that of FSOC.Our findings also suggest that enhancing FSOC could be more crucial than boosting inner resources like psychological resilience for directly alleviating negative psychological responses.Nevertheless, the significance of psychological resilience as a mediator in this dynamic is reaffirmed, suggesting that clinical practitioners should focus on bolstering both FSOC and psychological resilience to improve the psychological status and QoL of caregivers.

Strengths and limitations
This study explores the impact of a family-level coping resource, namely FSOC, on the QoL of caregivers.Extending the existing body of research that has examined the relationship between an individual's sense of coherence and health outcomes, our findings offer valuable insights for clinical practitioners seeking to enhance the support provided to caregivers of advanced cancer patients.Furthermore, we delve into the underlying mechanisms at play within the two dimensions of QoL (physical health and mental health).Our results confirm the applicability of a chain mediation model to these two dimensions.Therefore, enhancing family coherence can bolster individual resilience, reduce distress, and promote both physical and mental well-being.This holds significant promise for positively contributing to the overall health and well-being of caregivers within the context of advanced cancer.
However, several limitations exist.Firstly, the cross-sectional design constrains our ability to confirm causal links between variables and assess the long-terms effects of FSOC on caregiver outcomes.To address this, future studies should consider adopting longitudinal or experimental methodologies to deepen the understanding of these relationships.Additionally, conducting qualitative interviews with caregivers who have different relationships with advanced cancer patients could yield richer insights into the nuances of the caregiving experience and enhance the study's findings.Although the study controlled for certain demographic variables, it's important to acknowledge the potential influence of other confounding factors, including social support, coping strategies, cultural factors, and patient characteristics such as treatment status.Future research could benefit from a more comprehensive examination of these potential confounders.Moreover, while our research focused on the mediating roles of psychological resilience and distress, it's pivotal to recognize that the influence of FSOC on QoL might be shaped by other mediators or moderators, such as dyadic coping or family functioning, warranting further investigation.Furthermore, this study relied solely on self-report measures.Future studies could enhance the robustness of findings by employing a combination of self-report measures and objective assessments, such as physiological indicators and family environment assessments.Given that our samples primarily originated from tertiary oncology hospitals in one province through convenience sampling, there is a risk of selection bias, limiting the generalizability of findings to other healthcare settings or geographical locations.Future studies would benefit from a more diverse and representative sample base to facilitate holistic comparisons and longterm monitoring.Finally, assessing the applicability of the established mediation model to other chronic patient groups is an essential direction for future inquiries.

Conclusion
In summary, this research elucidates the processes through which FSOC bolsters the QoL of caregivers attending to advanced cancer patients.Importantly, FSOC not only directly amplifies caregivers' QoL but also has an indirect influence mediated by psychological distress.Additionally, the study unveils a chain mediation effect encompassing both psychological resilience and distress, further emphasizing the multifaceted ways in which FSOC can enhance caregivers' well-being.These findings deepen our comprehension of the intricate relationship between FSOC and QoL, emphasizing the potential benefits of interventions targeting FSOC enhancement and distress reduction to promote caregiver QoL.

Figure 1 .
Figure 1.Hypothesized conceptual model of the chain mediation.

Table 2
psychological resilience and distress influencing the association between FSOC and QoL.The model is further validated by the inclusion of QoL's two facets-physical and mental health-both of which conform to the chain mediation model.

Table 2 .
Correlations among family sense of coherence, psychological resilience, psychological distress, and quality of life.FSOC family sense of coherence, MH mental health, PD: psychological distress, PH physical health, PR psychological resilience, QoL quality of life, SD standard deviation.**P < 0.01.

Table 3 .
Testing the mediation effect of FSOC on QoL and physical health.FSOC family sense of coherence; a: b Vol:.(1234567890)ScientificReports | (2024) 14:10701 | https://doi.org/10.1038/s41598-024-61344-4www.nature.com/scientificreports/among other populations, motivating individuals to leverage both intrinsic and extrinsic resources to address challenges stemming from stressful events.These insights confirm FSOC's pivotal role in managing stress, preserving functionality, bolstering subjective well-being, and enhancing overall QoL, with a special focus on mental health.Our findings extend this understanding by demonstrating that FSOC positively influences not just mental health, but also physical well-being, especially in caregiving scenarios within chronic disease contexts.This underlines the indispensable nature of familial support in boosting caregivers' QoL.Hence, clinical nursing